Jane McCredie: Flu shot doubts

LIKE many people, I have had a somewhat lackadaisical approach to getting an annual influenza shot.

If it’s been offered free at my workplace, I’ve tended to do it. Otherwise, I mostly haven’t bothered.

As anybody who reads this blog regularly will know, I’m a strong supporter of immunisation, but that doesn’t mean I believe all vaccines are equal.

Whooping cough in children: absolutely. Influenza in healthy adults: not so sure.

The picture may be different in children or in adults with other risk factors (respiratory disease, for example), but Cochrane reviews don’t offer strong support for general influenza immunisation programs such as those offered by many employers.

A 2010 review of influenza vaccination in healthy adults found it had only a modest effect in reducing symptoms and working days lost, and no effect on transmission of disease or on complications such as pneumonia.

In Australia, the flu vaccine is recommended for all people over 65, although a 2009 Cochrane review found the evidence on immunisation in that age group was of poor quality and not capable of providing guidance on safety, efficacy or effectiveness.

A feature article published by the BMJ this month further questions the evidence for widespread influenza immunisation.

Dr Peter Doshi, a researcher at the medical school at Johns Hopkins University in the US, argues public health officials may have exaggerated the risks associated with the disease and overstated the benefits of the vaccine.

In fact, he describes the official rhetoric on influenza in his own country as an example of “disease-mongering”, comparing it with drug companies that try to convince us “we have underdiagnosed epidemics of erectile dysfunction, social anxiety disorder, and female sexual dysfunction, each with their own convenient acronym and an approved medication at the ready”.

Dr Doshi isn’t saying influenza is a figment of the imagination, or that immunisation against it is entirely without benefit, but he is asking for more rigour in assessing the risks and benefits of vaccinating.

One of the problems is that most studies of influenza immunisation have been observational, which obviously makes their findings less reliable.

If healthier people are more likely to immunise, it wouldn’t necessarily be surprising if studies found lower all-cause mortality rates in those who’d had the vaccine.

In fact, some studies have found reductions in all-cause mortality of up to 50% associated with influenza immunisation, prompting Dr Doshi to ask how flu shots could be preventing half of all deaths when the disease itself is only estimated to cause around 5% of deaths during the flu season.

It’s a reasonable question and the only way to answer it would be a properly designed randomised controlled trial conducted in a large enough population to provide reliable mortality data.

There may be other benefits from widespread immunisation, of course. It’s possible this has played a role in preventing flu pandemics: fewer circulating viruses in humans might mean less risk of recombination with animal viruses.

But the real problem is that we don’t have a clear picture of the risks and benefits of influenza immunisation in the general community.

And that’s what an evidence-based approach requires.

And while on the subject of immunisation, congratulations to SBS on their documentary, Jabbed, which aired last night. It was an intelligent look at the issues surrounding childhood immunisation.
 

Jane McCredie is a Sydney-based science and medicine writer.